Microwave induced rapid preparation of acetyl, trifluoroacetyl and tert-butyl dimethylsilyl derivatives of fatty alcohols and diacylglycerols for gas chromatography-mass spectrometric analysis

Abstract

Acetyl, trifluoroacetyl and tert-butyl dimethylsilyl derivatives of fatty alcohols and diacylglycerols are commonly used for structural characterization. The conventional techniques require 1 h of heating at 80°C for preparation of acetyl, 15 min of heating at 45°C for synthesis of trifluoroacetyl and 20 min of heating at 80°C for preparation of tert-butyl dimethylsilyl derivatives. Using a commercially available microwave oven and low power microwave irradiation, we prepared acetyl derivative in 40 s, trifluoroacetyl derivative in 10 s (fatty alcohol only) and tert-butyl dimethylsilyl derivative in 2 min. We observed quantitative conversion of fatty alcohols and diacylglycerol under microwave irradiation in all cases, except for conversion of diacylglycerol to its trifluoroacetyl derivative. However, the conventional technique did not lead to quantitative conversion either. The yields obtained by microwave irradiation and the conventional technique were comparable. The mass spectral fragmentation patterns of derivatives produced by microwave irradiation were identical to the fragmentation patterns of derivatives produced by the conventional technique. We conclude that the microwave oven can be used for rapid preparation of acetyl, trifluoroacetyl and tert-butyl dimethylsilyl derivatives of fatty alcohols and acetyl as well as tert-butyl dimethylsilyl derivatives of diacylglycerols.